1. Technical Field
The present disclosure relates to an adsorption refrigerator, a method for controlling the adsorption refrigerator, and a cooling system.
2. Description of the Related Art
An adsorption refrigerator is known as a thermal heat pump. In the adsorption refrigerator, a material called an adsorbent (e.g., a porous material such as silica gel or zeolite) is disposed inside a container of an adsorber. Water as an adsorbent refrigerant is adsorbed and desorbed, that is, a compressor operation is performed to move the refrigerant against a temperature gradient, so that a heat pump action is achieved.
In an adsorption process of the adsorber, an inside of the container is controlled in a reduced-pressure state by an appropriate vacuum pump. Thus, vapor having a low temperature (e. g., approximately 6° C.) is adsorbed by the adsorbent from an evaporator. Further, in the adsorption process of the adsorber, the adsorbent generates heat by adsorbing vapor. Thus, the heat of the adsorbent is removed by a cooling water from an appropriate heat exchanger (e.g., a cooling tower). Accordingly, the adsorbent is maintained at a temperature suitable for an adsorption performance of the adsorbent.
The adsorption of vapor is performed when the adsorbent is dry. However, the adsorbent becomes saturated with water vapor and stops the adsorption of vapor after a while. Thus, regeneration (recovery) of the adsorbent is required.
In a regeneration process of the adsorber, the adsorbent is heated by heat of an appropriate external heat source. When a temperature of the adsorbent increases by heating the adsorbent, moisture adhered to the adsorbent is detached (desorbed), so that the adsorption performance of the adsorbent recovers. The vapor separated from the adsorbent is cooled by heat exchange with a cooling water inside a condenser and returned as liquid water to the condenser.
In this manner, the vapor adsorption and the regeneration of the adsorbent are alternately performed in the adsorber of the adsorption refrigerator.
A conventional single effect adsorption refrigerator is typically provided with a pair of such adsorbers. When one of the adsorbers performs the adsorption process, the other adsorber performs the regeneration process. The single effect adsorption refrigerator is configured to continuously generate refrigeration output by timely switching between the adsorption process and the regeneration process.
Hereinbelow, a configuration and an operation of the single effect adsorption refrigerator will be described with reference to drawings. FIGS. 1 and 2 illustrate an example of the conventional single effect adsorption refrigerator.
Single effect adsorption refrigerator 100 includes a pair of adsorbers 101, 102 (hereinbelow, referred to as paired adsorbers 101, 102), refrigerant system 300, thermal system 400, and cooling water system 500.
In each of paired adsorbers 101, 102, an adsorbent such as silica gel or zeolite is filled in a container. Here, a pressure inside each of paired adsorbers 101, 102 is reduced to a pressure of approximately 1/100 atmospheres by a vacuum pump (not illustrated).
A flow path member passes through each of paired adsorbers 101, 102. A heating medium (e.g., water) which performs heat exchange with the adsorbent flows through the flow path member. That is, the flow path member includes a heat exchange member such as a heat exchange fin or a heat exchange coil.
Three-way valves 121, 123 are disposed near an exit and an entrance of the flow path member of adsorber 101 so as to timely supply a high-temperature heating medium which circulates through circulation path 120 of thermal system 400 to adsorber 101 and to timely supply a cooling water which circulates through circulation path 130 of cooling water system 500 to adsorber 101. That is, the exit and the entrance of adsorber 101 are connected to both of thermal system 400 and cooling water system 500 respectively through three-way valves 123, 121. Thus, single effect adsorption refrigerator 100 is configured to select whether to pass the heating medium or to pass the cooling water into adsorber 101.
Further, three-way valves 122, 124 are disposed near an exit and an entrance of the flow path member of adsorber 102 so as to timely supply the high-temperature heating medium which circulates through circulation path 120 of thermal system 400 to adsorber 102 and to timely supply the low-temperature cooling water which circulates through circulation path 130 of cooling water system 500 to adsorber 102. That is, the exit and the entrance of adsorber 102 are connected to both of thermal system 400 and cooling water system 500 respectively through three-way valves 124, 122. Thus, single effect adsorption refrigerator 100 is configured to select whether to pass the heating medium or to pass the cooling water into adsorber 102.
For example, an electromagnetic ball valve can be used as each of three-way valves 121, 122, 123, 124.
Paired adsorbers 101, 102 are connected to evaporator 115 respectively through two-way valves 111, 112 and also connected to condenser 116 respectively through two-way valves 113, 114.
For example, an electromagnetic or pneumatic butterfly valve can be used as each of two-way valves 111, 112, 113, 114.
FIG. 1 illustrates a state in which the adsorber 101 performs the adsorption process and the adsorber 102 performs the regeneration process. FIG. 2 illustrates a state in which the adsorber 101 performs the regeneration process and the adsorber 102 performs the adsorption process. That is, heating by the heating medium and cooling by the cooling water are alternately performed in paired adsorbers 101, 102.
In FIGS. 1 and 2, in order to facilitate understanding of details of the drawings, an open side of each of three-way valves 121, 122, 123, 124 is indicated in black, and a closed side of each of three-way valves 121, 122, 123, 124 is indicated in white for convenience. Further, each of two-way valves 111, 112, 113, 114 in an open state is indicated in black, and each of two-way valves 111, 112, 113, 114 in a closed state is indicated in white. Further, solid lines indicate circulation path 130 in a communicating state and a path for vapor adsorbed by the adsorbent. Dotted lines indicate circulation path 120 in a communicating state and a path for regeneration vapor. Thin two-dot chain lines indicate paths in a non-communicating state through which no heating medium flows.
Hereinbelow, single effect adsorption refrigerator 100 in a case where adsorber 101 performs the adsorption process and adsorber 102 performs the regeneration process will be described in more detail with reference to FIG. 1. Single effect adsorption refrigerator 100 of FIG. 2 can be easily understood from the following description. Thus, description for FIG. 2 will be omitted. Water is typically used as the heating medium of refrigerant system 300 and thermal system 400 of single effect adsorption refrigerator 100. Thus, the configuration and the operation of single effect adsorption refrigerator 100 that uses water as the heating medium will be described.
A water temperature in refrigerant system 300, a water temperature in thermal system 400, and a water temperature in cooling water system 500 differ from each other. As an example, the water temperature in refrigerant system 300 is approximately 15° C., the water temperature in thermal system 400 is approximately 80° C., and the water temperature in cooling water system 500 is approximately 30° C.
Respective ends of water path 110 in refrigerant system 300 are connected to evaporator 115 and condenser 116.
In evaporator 115, refrigeration output is taken out by evaporation of water inside evaporator 115. That is, cool water cooled by the evaporation of water can be fed to outside from evaporator 115.
In the present example, two-way valve 111 is open, and two-way valve 112 is closed. Thus, vapor generated in evaporator 115 is adsorbed by the adsorbent of adsorber 101.
In condenser 116, vapor generated in the regeneration process is cooled by circulating water flowing through circulation path 130 in cooling water system 500. Accordingly, condensed water is generated inside condenser 116. The condensed water is fed to evaporator 115 described above by power of pump 117 and reused as water for evaporation. In the present example, two-way valve 113 is closed, and two-way valve 114 is open. Thus, vapor generated in the regeneration process by adsorber 102 is supplied to condenser 116.
For example, a magnet pump or a cascade pump can be used as pump 117.
Heat source heat exchanger 125, adsorber 102, buffer tank 126, and pump 127 are disposed in this order in a circulating water flowing direction on circulation path 120 in thermal system 400. In heat source heat exchanger 125, circulating water flowing through circulation path 120 is used as a heat receiving fluid. Thus, heat can be taken into thermal system 400 from an appropriate heat source (that is, circulating water flowing through circulation path 120 is heated). In the present example, high-temperature circulating water that has passed through heat source heat exchanger 125 in circulation path 120 is fed into adsorber 102 by valve operations of three-way valves 121, 122, 123, 124 and power of pump 127. Accordingly, the adsorbent of adsorber 102 is heated by heat exchange with the high-temperature circulating water, so that the regeneration process of adsorber 102 is performed.
For example, a magnet pump or a cascade pump can be used as pump 127. Buffer tank 126 is a tank for buffer that temporarily stores hot water.
Heat source heat exchanger 131 (e.g., a cooling tower), pump 132, adsorber 101, and condenser 116 are disposed in this order in a circulating water flowing direction on circulation path 130 in the cooling water system 500. In heat exchanger 131, circulating water flowing through circulation path 130 is used as a heat applying fluid. Thus, heat is removed from circulating water in circulation path 130 when the circulating water passes through heat exchanger 131 (that is, the circulating water flowing through circulation path 130 is cooled). In the present example, low-temperature circulating water that has passed through heat exchanger 131 in circulation path 130 is fed into adsorber 101 by valve operations of three-way valves 121, 122, 123, 124 and power of pump 132. Accordingly, the adsorbent of adsorber 101 is cooled by heat exchange with the low-temperature circulating water and maintained at a temperature suitable for the adsorption process. The circulating water that has passed through an inside of the adsorber 101 is used for cooling vapor generated in the regeneration process in condenser 116 described above.
For example, a magnet pump or a cascade pump can be used as pump 132.
In this manner, in single effect adsorption refrigerator 100, when adsorber 101 performs the adsorption process, adsorber 102 performs the regeneration process. Single effect adsorption refrigerator 100 continuously generates refrigeration output by timely switching between the adsorption process and the regeneration process.
The switching described above may be, for example, a system that previously fixes a cycle time or a system that performs control based on a temperature of each of paired adsorbers 101, 102. In the latter case, it is preferred that a pair of temperature detectors (not illustrated) be disposed near the exit and the entrance of the flow path member of adsorber 101, and a pair of temperature detectors (not illustrated) be disposed near the exit and the entrance of the flow path member of adsorber 102. That is, a state of the adsorption process and a state of the regeneration process of paired adsorbers 101, 102 can be understood from a difference in temperatures detected by the pair of temperature detectors (hereinbelow, referred to as a detected temperature difference). For example, when vapor adsorption by the adsorbent has been completely stopped, and the adsorbent has been completely regenerated, the detected temperature difference becomes zero in theory.
Next, double effect of an adsorption refrigerator will be described. So-called double effect of a refrigeration cycle is a system that uses exhaust heat obtained from a first adsorption refrigeration cycle at a side where an operating temperature is high to drive a second adsorption refrigeration cycle at a side where the operating temperature is low in a thermal heat pump.
For example, in an absorption refrigerator, a double effect cycle of a condensation heat recovery system is commonly known. In the double effect cycle of the condensation heat recovery system, regeneration of a low-temperature regenerator is performed by condensation heat of high-temperature regeneration vapor obtained from a high-temperature regenerator. In this case, a coefficient of performance (COP) of the double effect cycle is calculated from a theoretical formula of (Formula 1) described below.ε0=ε1+(ε1×ε2)=ε1×(1+ε2)  (Formula 1)
In (Formula 1), ε0 is the COP of the double effect cycle, ε1 is a single effect COP of a first refrigeration cycle, and ε2 is a single effect COP of a second refrigeration cycle.
A COP of a single effect absorption refrigerator is approximately 0.6. Thus, when the single effect COP of the first refrigeration cycle and the single effect COP of the second refrigeration cycle are both 0.6, ε0=0.96 is calculated by substituting the single effect COPs into (Formula 1). That is, the double effect cycle has a COP that is higher by approximately 60% than the single effect cycle.
It is known that the double effect cycle can also be applied to an adsorption refrigerator similarly to the absorption refrigerator described above. In the adsorption refrigerator, in addition to the double effect by the condensation heat recovery system described above, double effect by an adsorption heat recovery system can be employed (e.g., refer to NPL 1).
NPL 1 discloses that the double effect by the adsorption heat recovery system can achieve a higher efficiency than the double effect by the condensation heat recovery system by selecting an appropriate adsorbent.
Adsorption heat is generated with vapor adsorption by an adsorbent in an adsorption process in an adsorber of an adsorption refrigerator. That is, the adsorption heat is generated as a result of that water vapor sucked to an adsorber is adsorbed by the adsorbent and loses kinetic energy. Thus, the adsorption heat is equal in heat quantity to condensation heat generated in the regeneration process of the adsorber. The double effect by the adsorption heat recovery system is a system that recovers the adsorption heat by a heating medium and regeneration-drives the second adsorption refrigeration cycle by the heat recovered by the heating medium.